1. Field of the Invention
The present invention relates generally to optical fiber structures having multiple cores, and particularly to a method for creating optical fiber structures with separable cores, the multi-core structures formed thereby, and uses for such separable multi-core structures.
2. Technical Background
Many applications for optical devices and components, particularly those used in telecommunications (such as Mach-Zehnder interferometers, couplers, and cascaded multi-port add/drop multiplexers), require the use of multiple fibers in which closely-spaced fiber cores are arranged in a variety of configurations. However, these fibers cannot be easily interconnected with other optical fibers or components which require pigtailing or splicing to the fibers. One solution has been to create optical fibers having multiple cores (multi-core fibers) from individual fibers by fusing these individual fibers together. However, this solution mitigates against efficient production of components, can have a detrimental effect on the individual fibers or cores in the areas or interfaces where the fibers are fused, and require greater design work and experimentation to accommodate the impact which fusing the fibers will have on the optical properties of the resulting component.
Using a plurality of separate fibers to achieve the desired interconnects typically involves employing a V-groove or other alignment structure to align the individual fibers with opposing fibers, collimating lenses, or waveguides on an integrated optical (or xe2x80x9cplanarxe2x80x9d) component. These substrates and alignment structures are expensive and difficult to fabricate and assemble with the necessary optical alignment tolerances (on the order of 0.1 micron), and often do not align the fibers with high precision when a large number of fibers are involved.
The configuration of the cores in multiple core optical fiber ribbons or bundles are typically dictated by several factors such as the availability and suitability of fiber draw equipment and processes, as well as the optical components with which the optical fibers are to be coupled and the ferrules to be used for receiving and securing the optical fibers.
The present invention is therefore directed to a separable multi-core optical fiber structure, and a method of making such fibers, which substantially overcomes one or more of the limitations and disadvantages of the related art.
The present invention provides an optical fiber having multiple cores which allows simple and precise interconnections to both a planar and fiber structures which require pigtailing or splicing. The present invention also provides a method for efficiently making such a multi-core fiber and separating the multiple-cores from one another for pigtailing or splicing to other fibers (such as input and output fibers in a multi-fiber or multi-port device). The present invention also permits effective control over the spacing between the adjacent cores in the multi-core optical fiber structure.
The present invention may be realized by providing a separable multi-core fiber structure including a plurality of fibers attached together with an attachment height between adjacent fibers small enough to allow fibers to be separated at at least one point along structure, and large enough to maintain a multi-core fiber along the remainder of the structure.
The separable multi-core fiber structure may include a spacer formed between outer fibers and fibers adjacent to the outer fibers. In one embodiment, the spacer may be fashioned as a dummy rod between each of the outer canes and adjacent canes, with the outer canes having a larger diameter than the inner canes. Alternately, the separable multi-core fiber structure may include dummy fibers adjacent to each outer fiber.
The method of the present invention for making an optical fiber structure having multiple cores includes tacking a plurality of canes together to form a tacked preform assembly, and consolidating and drawing the tacked preform assembly to desired dimensions while controlling the attachment height between canes to form the fiber structure.
The method of the present invention for using the separable multi-core optical fiber structures may include separating individual fiber cores at one end of the fiber structure after consolidating and drawing. In one embodiment, the separating process may include etching between the adjacent fibers to be separated. Alternately, the separating process may involve separating fibers at both ends of the fiber structure with the fibers remaining attached at some intermediate point of the fiber structure, or separating the fibers along substantially the entire length of the fiber structure while retaining one end of the fiber structure intact.
These advantages and uses of the present invention will become more readily apparent from the detailed description given hereinafter, taken together with the appended drawing Figures. However, it should be understood that the detailed description and specific examples, while indicating the generally preferred embodiments of the invention, are given by way of illustration only, since various changes, modifications, variations, and alterations within the spirit and scope of the invention will become apparent to those skilled in the art from this detailed description.